Near surface deformation associated with the scratch in polypropylene–clay nanocomposite: A microscopic study

The near surface deformation during scratching of neat polypropylene (PP) and polymer nanocomposites (PP–clay) at loads of 0.2–6 kgf is described in terms of characteristics of scratch morphology and scratch deformation parameters. In neat PP, the application of higher loads introduces severe ironing deformation, disrupting the periodic parabolic nature of scratch tracks such that the material plastically flows along the ironing zone. Under identical test conditions, the severity of surface deformation in PP–clay nanocomposites, which leads to stress whitening is significantly reduced. At lower loads, the periodic nature of tracks is retained together with ironing, while at higher loads, ploughing occurred. The resistance to scratch deformation is discussed in terms of modulus, elastic recovery, and scratch hardness.